From 4aea03d8d5180a65f161ff37cac21424557ca04c Mon Sep 17 00:00:00 2001
From: Lassier Antoine <toinousp@gmail.com>
Date: Fri, 10 Nov 2023 22:21:11 +0100
Subject: [PATCH] feat: added simple pkce and state checks for auth0

---
 src/runtime/server/lib/oauth/auth0.ts | 62 ++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 2 deletions(-)

diff --git a/src/runtime/server/lib/oauth/auth0.ts b/src/runtime/server/lib/oauth/auth0.ts
index abe7b499..1ffff02a 100644
--- a/src/runtime/server/lib/oauth/auth0.ts
+++ b/src/runtime/server/lib/oauth/auth0.ts
@@ -4,6 +4,7 @@ import { withQuery, parsePath } from 'ufo'
 import { ofetch } from 'ofetch'
 import { defu } from 'defu'
 import { useRuntimeConfig } from '#imports'
+import crypto from 'crypto'
 
 export interface OAuthAuth0Config {
   /**
@@ -23,7 +24,7 @@ export interface OAuthAuth0Config {
   domain?: string
   /**
    * Auth0 OAuth Audience
-   * @default process.env.NUXT_OAUTH_AUTH0_AUDIENCE
+   * @default ''
    */
   audience?: string
   /**
@@ -38,19 +39,37 @@ export interface OAuthAuth0Config {
    * @default false
    */
   emailRequired?: boolean
+  /**
+   * checks
+   * @default []
+   * @see https://auth0.com/docs/flows/authorization-code-flow-with-proof-key-for-code-exchange-pkce
+   * @see https://auth0.com/docs/protocols/oauth2/oauth-state
+   */
+  checks?: OAuthChecks[]
 }
 
+type OAuthChecks = 'pkce' | 'state'
 interface OAuthConfig {
   config?: OAuthAuth0Config
   onSuccess: (event: H3Event, result: { user: any, tokens: any }) => Promise<void> | void
   onError?: (event: H3Event, error: H3Error) => Promise<void> | void
 }
 
+function base64URLEncode(str: string) {
+  return str.replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '')
+}
+function randomBytes(length: number) {
+  return crypto.randomBytes(length).toString('base64')
+}
+function sha256(buffer: string) {
+  return crypto.createHash('sha256').update(buffer).digest('base64')
+}
+
 export function auth0EventHandler({ config, onSuccess, onError }: OAuthConfig) {
   return eventHandler(async (event: H3Event) => {
     // @ts-ignore
     config = defu(config, useRuntimeConfig(event).oauth?.auth0) as OAuthAuth0Config
-    const { code } = getQuery(event)
+    const { code, state } = getQuery(event)
 
     if (!config.clientId || !config.clientSecret || !config.domain) {
       const error = createError({
@@ -65,6 +84,19 @@ export function auth0EventHandler({ config, onSuccess, onError }: OAuthConfig) {
 
     const redirectUrl = getRequestURL(event).href
     if (!code) {
+      // Initialize checks
+      const checks: Record<string, string> = {}
+      if (config.checks?.includes('pkce')) {
+        const pkceVerifier = base64URLEncode(randomBytes(32))
+        const pkceChallenge = base64URLEncode(sha256(pkceVerifier))
+        checks['code_challenge'] = pkceChallenge
+        checks['code_challenge_method'] = 'S256'
+        setCookie(event, 'nuxt-auth-util-verifier', pkceVerifier, { maxAge: 60 * 15, secure: true, httpOnly: true })
+      }
+      if (config.checks?.includes('state')) {
+        checks['state'] = base64URLEncode(randomBytes(32))
+        setCookie(event, 'nuxt-auth-util-state', checks['state'], { maxAge: 60 * 15, secure: true, httpOnly: true })
+      }
       config.scope = config.scope || ['openid', 'offline_access']
       if (config.emailRequired && !config.scope.includes('email')) {
         config.scope.push('email')
@@ -78,10 +110,35 @@ export function auth0EventHandler({ config, onSuccess, onError }: OAuthConfig) {
           redirect_uri: redirectUrl,
           scope: config.scope.join(' '),
           audience: config.audience || '',
+          ...checks
         })
       )
     }
 
+    // Verify checks
+    const pkceVerifier = getCookie(event, 'nuxt-auth-util-verifier')
+    setCookie(event, 'nuxt-auth-util-verifier', '', { maxAge: -1 })
+    const stateInCookie = getCookie(event, 'nuxt-auth-util-state')
+    setCookie(event, 'nuxt-auth-util-state', '', { maxAge: -1 })
+    if (config.checks?.includes('state')) {
+      if (!state || !stateInCookie) {
+        const error = createError({
+          statusCode: 401,
+          message: 'Auth0 login failed: state is missing'
+        })
+        if (!onError) throw error
+        return onError(event, error)
+      }
+      if (state !== stateInCookie) {
+        const error = createError({
+          statusCode: 401,
+          message: 'Auth0 login failed: state does not match'
+        })
+        if (!onError) throw error
+        return onError(event, error)
+      }
+    }
+
     const tokens: any = await ofetch(
       tokenURL as string,
       {
@@ -95,6 +152,7 @@ export function auth0EventHandler({ config, onSuccess, onError }: OAuthConfig) {
           client_secret: config.clientSecret,
           redirect_uri: parsePath(redirectUrl).pathname,
           code,
+          code_verifier: pkceVerifier
         }
       }
     ).catch(error => {